1. Field of the Invention
This invention relates to modification of electrode surfaces to enhance attachment of nucleic acids and proteins. More particularly, the invention relates to methods for making and preparing such electrodes for use in the detection of nucleic acid hybridization.
2. Description of the Related Art
One method to detect the presence of a target nucleic acid sequence in a sample is to immobilize a probe nucleic acid sequence that is complementary to the target sequence on or near the surface of an electrode. If the target nucleic acid sequence is present and conditions are favorable, the target sequence will hybridize with the complementary probe sequence. The electrochemical characteristics of the electrode will then be altered, allowing electrochemical detection of the hybridization of the target and probe nucleic acids.
Electrochemical detection of nucleic acid hybridization can be aided by the presence of a redox active species. For example, a redox active counterion to the probe and target nucleic acids can be used. The concentration of the redox active counterion near the electrode surface will be higher when the nucleic acids are hybridized as compared to when hybridization is not present. This increase in concentration will be reflected in the electrochemical response to the oxidation or reduction of the redox active counterion. Such an electrochemical quantitation technique is described in A. B. Steel et al., Electrochemical Quantitation of DNA Immobilized on Gold, Anal. Chem. 70:4670-77 (1998), hereby expressly incorporated by reference in its entirety. In this publication, Steel et al. describe the use of cobalt (III) trisbipyridyl and ruthenium (III) hexaamine as species which interact with surface-immobilized DNA.
Current methods of electrode fabrication result in background signals that interfere with accurate detection of nucleic acid hybridization in the presence of redox active species. Therefore, there is an unmet need for electrodes and systems that provide more accurate and precise detection of nucleic acid hybridization.